aws-cdk-lib.aws_lambda_nodejs module

Language	Package
.NET	Amazon.CDK.AWS.Lambda.Nodejs
Go	github.com/aws/aws-cdk-go/awscdk/v2/awslambdanodejs
Java	software.amazon.awscdk.services.lambda.nodejs
Python	aws_cdk.aws_lambda_nodejs
TypeScript	aws-cdk-lib » aws_lambda_nodejs

Amazon Lambda Node.js Library

This library provides constructs for Node.js Lambda functions.

Node.js Function

The NodejsFunction construct creates a Lambda function with automatic transpiling and bundling of TypeScript or Javascript code. This results in smaller Lambda packages that contain only the code and dependencies needed to run the function.

It uses esbuild under the hood.

Reference project architecture

The NodejsFunction allows you to define your CDK and runtime dependencies in a single package.json and to collocate your runtime code with your infrastructure code:

.
├── lib
│   ├── my-construct.api.ts # Lambda handler for API
│   ├── my-construct.auth.ts # Lambda handler for Auth
│   └── my-construct.ts # CDK construct with two Lambda functions
├── package-lock.json # single lock file
├── package.json # CDK and runtime dependencies defined in a single package.json
└── tsconfig.json

Example not in your language?

By default, the construct will use the name of the defining file and the construct's id to look up the entry file. In my-construct.ts above we have:

// automatic entry look up
const apiHandler = new nodejs.NodejsFunction(this, 'api');
const authHandler = new nodejs.NodejsFunction(this, 'auth');

Example not in your language?

Alternatively, an entry file and handler can be specified:

new nodejs.NodejsFunction(this, 'MyFunction', {
  entry: '/path/to/my/file.ts', // accepts .js, .jsx, .cjs, .mjs, .ts, .tsx, .cts and .mts files
  handler: 'myExportedFunc', // defaults to 'handler'
});

Example not in your language?

The handler value will be automatically prefixed with the bundled output file name, index., unless the handler value contains a . character, in which case the handler value is used as-is to allow for values needed by some Lambda extensions.

For monorepos, the reference architecture becomes:

.
├── packages
│   ├── cool-package
│   │   ├── lib
│   │   │   ├── cool-construct.api.ts
│   │   │   ├── cool-construct.auth.ts
│   │   │   └── cool-construct.ts
│   │   ├── package.json # CDK and runtime dependencies for cool-package
│   │   └── tsconfig.json
│   └── super-package
│       ├── lib
│       │   ├── super-construct.handler.ts
│       │   └── super-construct.ts
│       ├── package.json # CDK and runtime dependencies for super-package
│       └── tsconfig.json
├── package-lock.json # single lock file
├── package.json # root dependencies
└── tsconfig.json

Example not in your language?

Customizing the underlying Lambda function

All properties of lambda.Function can be used to customize the underlying lambda.Function.

See also the AWS Lambda construct library.

The NodejsFunction construct automatically reuses existing connections when working with the AWS SDK v2 for JavaScript. Set the awsSdkConnectionReuse prop to false to disable it.

The AWS SDK v3 for JavaScript does not include the environment variable set by awsSdkConnectionReuse. See this guide for information about reusing connections. Therefore, for runtimes >= Node 18, which include SDK v3, the prop defaults to false, and must be explicitly set to true in order for the environment variable to be set.

Runtime

When the @aws-cdk/aws-lambda-nodejs:useLatestRuntimeVersion feature flag is enabled, the NODEJS_LATEST runtime will be used by default. This runtime will be updated to use the latest Node.js version currently available in lambda. Since this runtime can change from version to version, you should ensure that all of your dependencies are included during packaging and avoid relying on depdendencies being globally installed. See externals for details.

When using NODEJS_LATEST runtime make sure that all of your dependencies are included during bundling, or as layers. Usage of globally installed packages in the lambda environment may cause your function to break in future versions. If you need to rely on packages pre-installed in the lambda environment, you must explicitly set your runtime.

This can be set via lambda.Runtime:

import { Runtime } from 'aws-cdk-lib/aws-lambda';

new nodejs.NodejsFunction(this, 'my-function', {
    runtime: Runtime.NODEJS_18_X,
});

Example not in your language?

With the @aws-cdk/aws-lambda-nodejs:useLatestRuntimeVersion disabled, the runtime will default to NODEJ_16_X.

Lock file

The NodejsFunction requires a dependencies lock file (yarn.lock, pnpm-lock.yaml, bun.lockb or package-lock.json). When bundling in a Docker container, the path containing this lock file is used as the source (/asset-input) for the volume mounted in the container.

By default, the construct will try to automatically determine your project lock file. Alternatively, you can specify the depsLockFilePath prop manually. In this case you need to ensure that this path includes entry and any module/dependencies used by your function. Otherwise bundling will fail.

Local bundling

If esbuild is available it will be used to bundle your code in your environment. Otherwise, bundling will happen in a Lambda compatible Docker container with the Docker platform based on the target architecture of the Lambda function.

For macOS the recommended approach is to install esbuild as Docker volume performance is really poor.

esbuild can be installed with:

$ npm install --save-dev esbuild@0

Example not in your language?

OR

$ yarn add --dev esbuild@0

Example not in your language?

If you're using a monorepo layout, the esbuild dependency needs to be installed in the "root" package.json file, not in the workspace. From the reference architecture described above, the esbuild dev dependency needs to be in ./package.json, not packages/cool-package/package.json or packages/super-package/package.json.

To force bundling in a Docker container even if esbuild is available in your environment, set bundling.forceDockerBundling to true. This is useful if your function relies on node modules that should be installed (nodeModules prop, see below) in a Lambda compatible environment. This is usually the case with modules using native dependencies.

Working with modules

Externals

When the NODEJS_LATEST runtime is used, no modules are excluded from bundling by default. This is because the runtime will change as new NodeJs versions become available in lambda, which may change what packages are vended as part of the environment.

When passing a runtime that is known to include a version of the aws sdk, it will be excluded by default. For example, when passing NODEJS_16_X, aws-sdk is excluded. When passing NODEJS_18_X, all @aws-sdk/* packages are excluded.

[!WARNING] The NodeJS runtime of Node 16 will be deprecated by Lambda on June 12, 2024. Lambda runtimes Node 18 and higher include SDKv3 and not SDKv2. Updating your Lambda runtime from <=Node 16 to any newer version will require bundling the SDK with your handler code, or updating all SDK calls in your handler code to use SDKv3 (which is not a trivial update). Please account for this added complexity and update as soon as possible.

This can be configured by specifying bundling.externalModules:

new nodejs.NodejsFunction(this, 'my-handler', {
  bundling: {
    externalModules: [
      '@aws-sdk/*', // Use the AWS SDK for JS v3 available in the Lambda runtime
      'cool-module', // 'cool-module' is already available in a Layer
    ],
  },
});

Example not in your language? Includes AWS SDK in the bundle asset by setting bundleAwsSDK to true. This will exclude SDK from the external module and would not be resolved to Lambda provided SDK.

new nodejs.NodejsFunction(this, 'my-handler', {
  bundling: {
    bundleAwsSDK: true,
  },
});

Example not in your language?

Install modules

By default, all node modules referenced in your Lambda code will be bundled by esbuild. Use the nodeModules prop under bundling to specify a list of modules that should not be bundled but instead included in the node_modules folder of the Lambda package. This is useful when working with native dependencies or when esbuild fails to bundle a module.

new nodejs.NodejsFunction(this, 'my-handler', {
  bundling: {
    nodeModules: ['native-module', 'other-module'],
  },
});

Example not in your language?

The modules listed in nodeModules must be present in the package.json's dependencies or installed. The same version will be used for installation. The lock file (yarn.lock, pnpm-lock.yaml, bun.lockb or package-lock.json) will be used along with the right installer (yarn, pnpm, bun or npm).

When working with nodeModules using native dependencies, you might want to force bundling in a Docker container even if esbuild is available in your environment. This can be done by setting bundling.forceDockerBundling to true.

Configuring esbuild

The NodejsFunction construct exposes esbuild options via properties under bundling:

new nodejs.NodejsFunction(this, 'my-handler', {
  bundling: {
    minify: true, // minify code, defaults to false
    sourceMap: true, // include source map, defaults to false
    sourceMapMode: nodejs.SourceMapMode.INLINE, // defaults to SourceMapMode.DEFAULT
    sourcesContent: false, // do not include original source into source map, defaults to true
    target: 'es2020', // target environment for the generated JavaScript code
    loader: { // Use the 'dataurl' loader for '.png' files
      '.png': 'dataurl',
    },
    define: { // Replace strings during build time
      'process.env.API_KEY': JSON.stringify('xxx-xxxx-xxx'),
      'process.env.PRODUCTION': JSON.stringify(true),
      'process.env.NUMBER': JSON.stringify(123),
    },
    logLevel: nodejs.LogLevel.ERROR, // defaults to LogLevel.WARNING
    keepNames: true, // defaults to false
    tsconfig: 'custom-tsconfig.json', // use custom-tsconfig.json instead of default,
    metafile: true, // include meta file, defaults to false
    banner: '/* comments */', // requires esbuild >= 0.9.0, defaults to none
    footer: '/* comments */', // requires esbuild >= 0.9.0, defaults to none
    charset: nodejs.Charset.UTF8, // do not escape non-ASCII characters, defaults to Charset.ASCII
    format: nodejs.OutputFormat.ESM, // ECMAScript module output format, defaults to OutputFormat.CJS (OutputFormat.ESM requires Node.js >= 14)
    mainFields: ['module', 'main'], // prefer ECMAScript versions of dependencies
    inject: ['./my-shim.js', './other-shim.js'], // allows to automatically replace a global variable with an import from another file
    esbuildArgs: { // Pass additional arguments to esbuild
      "--log-limit": "0",
      "--splitting": true,
    },
  },
});

Example not in your language?

Command hooks

It is possible to run additional commands by specifying the commandHooks prop:

// This example only available in TypeScript
// Run additional props via `commandHooks`
new nodejs.NodejsFunction(this, 'my-handler-with-commands', {
  bundling: {
    commandHooks: {
      beforeBundling(inputDir: string, outputDir: string): string[] {
        return [
          `echo hello > ${inputDir}/a.txt`,
          `cp ${inputDir}/a.txt ${outputDir}`,
        ];
      },
      afterBundling(inputDir: string, outputDir: string): string[] {
        return [`cp ${inputDir}/b.txt ${outputDir}/txt`];
      },
      beforeInstall() {
        return [];
      },
      // ...
    },
    // ...
  },
});

Example not in your language?

The following hooks are available:

• beforeBundling: runs before all bundling commands
• beforeInstall: runs before node modules installation
• afterBundling: runs after all bundling commands

They all receive the directory containing the lock file (inputDir) and the directory where the bundled asset will be output (outputDir). They must return an array of commands to run. Commands are chained with &&.

The commands will run in the environment in which bundling occurs: inside the container for Docker bundling or on the host OS for local bundling.

Pre Compilation with TSC

In some cases, esbuild may not yet support some newer features of the typescript language, such as, emitDecoratorMetadata. In such cases, it is possible to run pre-compilation using tsc by setting the preCompilation flag.

new nodejs.NodejsFunction(this, 'my-handler', {
  bundling: {
    preCompilation: true,
  },
});

Example not in your language?

Note: A tsconfig.json file is required

Customizing Docker bundling

Use bundling.environment to define environments variables when esbuild runs:

new nodejs.NodejsFunction(this, 'my-handler', {
  bundling: {
    environment: {
      NODE_ENV: 'production',
    },
  },
});

Example not in your language?

Use bundling.buildArgs to pass build arguments when building the Docker bundling image:

new nodejs.NodejsFunction(this, 'my-handler', {
  bundling: {
    buildArgs: {
      HTTPS_PROXY: 'https://127.0.0.1:3001',
    },
  }
});

Example not in your language?

Use bundling.dockerImage to use a custom Docker bundling image:

new nodejs.NodejsFunction(this, 'my-handler', {
  bundling: {
    dockerImage: DockerImage.fromBuild('/path/to/Dockerfile'),
  },
});

Example not in your language?

This image should have esbuild installed globally. If you plan to use nodeModules it should also have npm, yarn, bun or pnpm depending on the lock file you're using.

Use the default image provided by aws-cdk-lib/aws-lambda-nodejs as a source of inspiration.

You can set additional Docker options to configure the build environment:

new nodejs.NodejsFunction(this, 'my-handler', {
 bundling: {
     network: 'host',
     securityOpt: 'no-new-privileges',
     user: 'user:group',
     volumesFrom: ['777f7dc92da7'],
     volumes: [{ hostPath: '/host-path', containerPath: '/container-path' }],
  },
});

Asset hash

By default the asset hash will be calculated based on the bundled output (AssetHashType.OUTPUT).

Use the assetHash prop to pass a custom hash:

<small class="code-sample-anno">[Example not in your language?](https://docs.aws.amazon.com/cdk/latest/guide/multiple_languages.html)</small>ts
new nodejs.NodejsFunction(this, 'my-handler', {
  bundling: {
    assetHash: 'my-custom-hash',
  },
});

If you chose to customize the hash, you will need to make sure it is updated every time the asset changes, or otherwise it is possible that some deployments will not be invalidated.

Docker based bundling in complex Docker configurations

By default the input and output of Docker based bundling is handled via bind mounts. In situtations where this does not work, like Docker-in-Docker setups or when using a remote Docker socket, you can configure an alternative, but slower, variant that also works in these situations.

new nodejs.NodejsFunction(this, 'my-handler', {
 bundling: {
   bundlingFileAccess: BundlingFileAccess.VOLUME_COPY,
 },
});

Example not in your language?

Running a custom build script as part of cdk synthesis

If you need more control over bundling -- or the build process in general -- then we include the ability to invoke your own build script. For example, if you have the following build.mjs file:

import * as path from 'path';
import { fileURLToPath } from 'url';
import esbuild from "esbuild";
import { cache } from "esbuild-plugin-cache";
import time from "esbuild-plugin-time";

const __filename = fileURLToPath(import.meta.url); // get the resolved path to the file
const __dirname = path.dirname(__filename); // get the name of the directory

await esbuild
  .build({
    entryPoints: [path.join(__dirname, 'handler', 'index.ts')],
    outfile: path.join(__dirname, 'build-output', 'index.js'),
    external: ['@aws-sdk/*', 'aws-sdk'],
    format: 'cjs',
    platform: 'node',
    target: 'node18',
    bundle: true,
    minify: true,
    plugins: [time(), cache({ directory: ".cache" })],
  })
  .catch((error) => {
    console.log(error);
    process.exit(1)
  });

Example not in your language?

then you could use build.mjs in a cdk construct as follows:

export class ExampleStack extends Stack {
  public constructor(scope: Construct, id: string, props?: StackProps) {
    super(scope, id, props);

    const pathToBuildFile = path.join(__dirname, 'build.mjs');

    // assuming the `handler` property is specified as 'index.handler' (as in this example), then
    // this 'build-output' directory must contain an index.js file with an exported `handler` function.
    const pathToOutputFile = path.join(__dirname, 'build-output');
    const handler = 'index.handler';

    const commandThatIsRanDuringCdkSynth = ['node', pathToBuildFile];
    const code = lambda.Code.fromCustomCommand(
      pathToOutputFile,
      commandThatIsRanDuringCdkSynth,
    );

    new nodejs.NodejsFunction(this, 'NodejsFunctionBuild', {
      code,
      handler,
    });
  }
}

Example not in your language?

where the build-output would be a directory that contains an index.js file with an exported handler function.